Orientation-blow molding equipment

ABSTRACT

In orientation-blow molding equipment, improved heating equipment is used for evenly and uniformly heating an injection molded piece under optimum temperature conditions for the succeeding biaxial orientation, with the aid of an improved jig which contributes to an efficient reheating and molding of the piece.

BACKGROUND OF THE INVENTION

The present invention relates to equipment for producing thin-walled andtransparent plastic containers having a high impact resistance byorientation-blowing polyethylene terephthalate.

In ordinary blow molding processes, the upper and lower parts of anextruded parison are held by a mold and compressed air is blown into thethus held parison to radially expand the same for forming it into acontainer or the like product.

In such processes, however, since the parison is oriented onlyuniaxially, the resultant products are inevitably inferior in theirstrength or transparency. Accordingly, a so-called orientation-blowmolding process in which a parison is oriented both laterally andlongitudinally produces a blow-molded container having an increasedstrength and toughness as well as improved gas impermeability andtransparency. The orientation-blow molding can be roughly divided intoan extrusion blow molding process using an extruded parison and aninjection blow molding process using an injected parison. The extrusionblow molding process is rather complicated because it requires moresteps including pipe extrusion, cooling and cutting to obtain a coldparison, reheating of the parison, top and bottom forming, longitudinalorientation, and blowing. While, the injection blow molding isrelatively simple because it contains a less number of steps such asparison injection, cooling, reheating, longitudinal orientation, andblowing. The present invention is based on the latter process, namely,injection blow molding.

SUMMARY OF THE INVENTION

The present invention has as an object to provide equipment which canproduce in a simplified manner plastic containers having excellentstrength, toughness and transparency by allowing an injected parison (orinjection-molded piece) to be evenly heated and accurately oriented bothlaterally and longitudinally in the mold.

Another object of the present invention is to facilitate processingoperations in the aforesaid molding equipment.

In the prior art orientation-blow molding process as describedpreviously, such plastic materials, for example polyethyleneterephthalate, have a high crystallizability and show a high rate ofcrystallization at molding temperatures. The resultant products cannothave a uniform quality because they are susceptible to post-moldingshrinkage. Intrinsically, polyethylene terephthalate has a highcrystallizability, thermal resistance and weathering as well as chemicalresistance, and has a wide range of application to transparent films andtextile fibers. In producing containers from polyethylene terephthalateby biaxially orienting the material, it is very important to maintainthe material temperature within a range suitable for the orientation.The inventors have successfully improved heating apparatus for thematerial to be oriented so as to secure an even and uniform heatingfunction.

The material to be processed in the equipment according to the presentinvention is a polyethylene terephthalate polymer having an intrinsicviscosity of at least 0.55 or its crystallizable copolymer or mixedpolymer. This polymer is first molded through an injection moldingmachine into an injected parison or injection-molded piece (hereinafter,shall be briefly referred to as piece) of a cylindrical shape having around closed-end. Preferably, the resultant piece has a crystallinity of4-7%. This is because if its crystallinity is lower than 4% a sufficientorientation cannot be achieved, while if its crystallinity is higherthan 7% it cannot produce a container having the required strength whenprocessed through the succeeding biaxial orientation. Thus, an injectedpiece of polyethylene terephthalate polymer having a crystallinity ofnearly 5% will result in a desired result.

The aforesaid plastic piece is fed into a heating chamber to be heatedto a temperature lower than the crystalline melting point of the plasticmaterial, namely, in the range of 140°-220° C. before being transferredto the succeeding blow-molding step. In the heating chamber, a largenumber of core metals for holding a jig to be described later aredisposed so that they can be recirculated. Further, several sets of bareheaters and heat exhausting dampers are disposed along the course of therecirculated core metals in such a manner that they divide the heatingchamber into several temperature zones for permitting the heatingtemperature to be controlled stepwise thereby. For example, the firstzone has a maintained temperature of 140°-160° C., the second zone amaintained temperature of 160°-190° C., the third zone a maintainedtemperature of 200°-220° C., and the fourth zone a maintainedtemperature of 180°-200° C.

The plastic piece passes through the heating and molding processes whilebeing attached to the jig with its neck portion side down. In theheating process, such special core metals that advance in the heatingchamber while holding the mandrel of the jig and that can impart arotational movement to the jig are used for heating the piece evenly anduniformly. The jig is composed mainly of a mandrel, neck support andcore shaft for orientation. The mandrel is that part of the jig which isengaged with holding parts of a conveyor, core metals, loading andunloading devices and also functions to support the piston of the coreshaft. The neck support is used to hold the neck of the piece andconstitutes and embracing (closing) part together with the mold. Thecore shaft is provided to longitudinally orient the piece by an upwardmovement of a cylindrical rod disposed at the underside and to radiallyorient the piece by introducing compressed air through air holes formedin the core shaft into the piece, in a state in which the jig is placedin the mold. Those parts to be assembled onto the jig other than themandrel may be changed in accordance with the shape and size of themoldings.

Prevention of an irregular temperature distribution due to partialcooling of the heated piece when it is transferred from the heatingapparatus to the mold gives a desirable result for the succeedingbiaxial orientation. For this purpose, according to the presentinvention, a shielding plate which is synchronously rotated withoutcontacting the piece moving from the exit of the heating apparatus isprovided for preventing the piece, coming out from the exit with no morerotation, from being partially heated.

The mold is provided in plurality spaced at an equal interval on theperipheral part of a large turntable which is tactically rotated. Eachmold can be separated into two sections along the longitudinaldirection, as usual. At the lower part of the mold, there are provided apiston rod which moves upwardly, the core shaft of the jig for axiallyorienting the piece and a compressed air feeding device for radiallyorienting the piece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a relationship between thecomponents of orientation-blow molding equipment according to thepresent invention;

FIG. 2 is a partially broken plan view of the equipment according to thepresent invention;

FIG. 3 is a longitudinal section of a heating apparatus used in thepresent invention;

FIG. 4 is a front view of an injected parison (piece) used in thepresent invention;

FIG. 5 is a partially broken front view of the jig according to thepresent invention, showing its state in which the piece is attachedthereto;

FIG. 6 is a section of a core metal used in the present invention;

FIG. 7 is a plan view of the core metal of FIG. 6;

FIG. 8 is a plan view of a brake device used in the present invention;

FIG. 9 is a longitudinal section of the mold showing a state in whichthe piece is longitudinally oriented;

FIG. 10 is a similar longitudinal section of the mold showing a state inwhich the piece is laterally oriented; and

FIG. 11 is a perspective of a product container which is molded by theequipment according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description of the preferred embodiments of the presentinvention, a case in which polyethylene terephthalate is used as theplastic material and its injected parison (piece) having a shape of aclosed-end cylinder is biaxially oriented to be formed into atransparent thin-walled container.

Referring now to the accompanying drawings, especially, to FIG. 1 itillustrates the components of the orientation-blow molding equipmentaccording to the present invention in the sequence of processing steps.The piece 10 having a closed-end cylindrical shape which is prepared bythe preceding injection molding step and cooled is set upside down ontoa jig which is carried in on a conveyor 11 and, then, the jig with thepiece is fitted by a transfer apparatus 12 onto a core metal which isrecirculated in the heating chamber 13. In the heating chamber 13, thepiece 10 is heated at a temperature lower than the crystalline meltingpoint of polyethylene terephthalate so as to avoid causing irregulartemperature distribution in it. At the exit of the heating chamber 13,to avoid the thus heated piece 10 from being partially cooled, it isgiven a rotational movement by the core metal and, as it is rotated, itis loaded by loading equipment into the mold of an orientation-blowmolding machine 15. Immediately after the mold is closed, an orientingmeans (core shaft) extending in the axial direction of the piece isactuated to axially (longitudinally) orient the same and, then,compressed air is blown into the piece to radially (laterally) orientit. Thereafter, the mold is opened, and the jig holding the thusbiaxially oriented piece is taken out by unloading equipment 16. The jigand piece are transferred onto the conveyor 11, where a molded container20 is released from the jig. The thus separated jig is returned on theconveyor 11 to the original piece setting step.

[INJECTION-MOLDED PIECE]

The injection-molded piece 10 is an intermediate molding cooled to anambient temperature after being molded by an injection molding machine(not shown). As shown in FIG. 4, it has a round bottom 17 at its upperend (as seen in FIG. 4) and a circular protrusion 19 for mounting latera cap (not shown) of the container along its periphery in closeproximity to its neck opening 18. Also, the piece has a barrel portion21 having its diameter gradually reduced from the neck opening 18 towardthe bottom 17.

[SUMMARY OF THE ORIENTATION-BLOW MOLDING EQUIPMENT]

Referring now to FIG. 2 which is a plan view in its entirety of theorientation-blow molding equipment according to the present invention,the molding equipment according to the present invention mainlycomprises a conveyor 11, transfer apparatus 12, heating chamber 13,loading equipment 14, orientation-blow molding machine 15, and unloadingequipment 16.

The conveyor 11 comprises an endless chain 22 which is provided with aplurality of attachment hooks 23 equally spaced apart from each otherand each having an almost rectangular U-shape. These attachments supporta mandrel 26 of a jig 25 to be described later. The aforementioned piece10 is set onto the jig 25 which is carried by the conveyor 11. That isto say, as shown in FIG. 5, the piece 10 is held in its invertedposition so that the neck opening 18 of the piece 10 is positioned atthe neck support 27 of the jig 25.

[JIG]

As shown in FIG. 5, the jig 25 mainly comprises the mandrel 26, necksupport 27, a core guide 28, spacer ring 29, and core shaft 30 fororientation.

The mandrel 26 is composed of a disk 31 of sword-guard shape, a cylinder32 extending downward from the disk 31, and a circular groove 33 formedbetween the disk 31 and cylinder 32. The neck support 27 has thefunction of supporting the outside of the neck opening 18 and isdisposed above a heat-insulating plate 34 provided on the top of thedisk 31 of the mandrel 26. The core guide 28 which is disposed in theneck support 27 is made of Teflon or like synthetic material forpermitting the core shaft 30 passing through the center thereof to beguided smoothly in its upward or downward movement. Onto the undersideof the core guide 28, there is fitted a spacer ring 29 for adjusting thestroke of the core shaft 30. While, at the upper end of the core shaft30, there is provided a core top 35 made of a heat-insulating material(e.g. Teflon) having an inverted taper shape (inverted frusto-conicalshape) for cutting off the heat conduction to and from the piece 10 andfor preventing the latter from sticking onto the core shaft when it issubjected to the longitudinal orientation. Also, the core shaft 30 isprovided at its lower end with a nozzle holder 36 of piston shape whichis fitted into the cylinder 32 of the mandrel 26. Inside the lower partof the core shaft 30, a hole of T-shape in section is bored, and two airpassages 30 of spline shape extend along the outside surface of theshaft upwards from the transverse openings 38 of the T-shape hole 37.

Instead of air passages 39 being of spline groove shape, a passage couldpass through the center of the core shaft 30. However, since the blowpressure used in the equipment is as high as 50 kg/cm², a sufficientwall thickness and, therefore, mechanical strength cannot be obtainedwith such a core shaft of hollow structure having a central air passage.Also, since pores would have to be provided at right angle or obliquelyto the side wall in such a hollow type core shaft, air jets directedoutwardly from such pores causes dimple flaws on the inner wall surfaceof the piece. While, if the air passages are of spline shape on theoutside surface of the core shaft as are the air passages 39 accordingto the present invention, air jets are not concentrated locally and,thus, the inner wall of the piece is free of the possibility ofsuffering dimple flaws.

The jig 25 holding the piece 10 makes the rounds of all processing stepsand is used in a recirculated manner. The core shaft 30 of the jig 25 isloaded in the mold loading equipment 75 in the orientation process to bedescribed later and, as shown in FIG. 5, it is moved upwards by theactuation of a cylinder rod 88 provided on the mold for longitudinallyorienting the piece 10. Further, compressed air is blown from thecylinder rod 88 through the T-shape hole 37 and air passages 39 into theinside of the piece 10 for radially orienting the same.

[TRANSFER APPARATUS]

The jig 25 on which the piece 10 as shown in FIG. 4 is set is fed on theconveyor 11 to the transfer apparatus 12.

The transfer apparatus 12 is provided with an arm 40 which has at itsfront end a hook for holding the cylinder 32 of the jig 25 and which ispivotally rotated around a fulcrum 41. Inside the locus of the hookmotion there is, provided an arcuate guide rail 42 having a magneticpiece for imparting a slight rotational motion to the jig 25 being movedso as to cause it to be engaged with and held by the core metal 44 inthe heating chamber 13.

[CORE METAL]

The core metal as shown in FIGS. 6 and 7 comprises a hollow holder 46attached to a rotary disk 45 and a hollow shaft 48 held by the holder 46via a pair of bearings 47. An ejector pin 50 is inserted through thehollow shaft 48. Onto the lower end of the ejector pin 50, is fixed aring 49. A spring 51 for pulling down the shaft 48 is interposed in itscontracted state between the ring 49 and the lower end of the shaft 48.Onto the upper end of the ejector pin 50, is attached a disk having adiameter larger than that of the shaft 48 for stopping the lowering ofthe ejector pin 50. The ejector pin 50 is pushed upwardly by action of acam (not shown) to lift the jig 25 when the jig is to be removed fromthe core metal 44 at the exit of the heating chamber 13 in the manner tobe described later in detail.

At the lower end portion of the hollow shaft 48, there is provided apinion 54 which is engaged with a gear 53 as shown in FIG. 3. Thus, asthe gear 53 is rotated, the pinion 54 is also rotated. The upper part ofthe shaft 48 hold a cylindrical body 56 via a pair of bearings 55, and aportion of the cylindrical body 56 is extended so as to integrally forma support holder 57. The support holder 57 is slightly longer than thecylinder 32 of the jig 25 and has at its upper end an arcuate projection58 which engages with the circular groove 33 of the jig 25. Also, amagnetic piece 59 which magnetically attracts the cylinder 32 isattached to an almost central part of the support holder 32. Further, acam follower 60 of roller shape is mounted onto the upper end face ofthe cylindrical body 56 at a position thereon almost opposite to thesupport holder 57. This cam follower 60 is arranged so as to be broughtinto contact with a braking device 73 provided at the exit of theheating chamber 13 to be described herein below.

[HEATING CHAMBER]

As shown in FIGS. 2, 3 and 6, the heating chamber 13 comprises therotary disk 45 on which a plurality of core metals 44 are attached alongits peripheral edge and a cover 61 placed over it. The heating chamber13 is divided into several heating zones, for example four zones, i.e.,I, II, III and IV, which are disposed along the transfer course of thecore metals 44 covered by the cover 61 and can be individuallycontrolled, so that the piece attached onto the jig 25 is heated underoptimum conditions for the succeeding orientation process.

In each heating zone, several (two, each one at an upper and lowerposition) bar heater elements comprising IR heating tubes 62 arehorizontally provided on the interior side of the transfer course of themetals 44. While, on the exterior side of the transfer course, aplurality of IR heating tubes 63 are vertically provided. Also, aheat-exhaust damper unit 64 is provided on the upper side of the cover61 at each heating zone. That is to say, a set of two heat-exhaustingstacks is provided and a damper 66 is pivotally mounted in eachheat-exhausting stack on a shaft 67 which is associated with a drivingdevice 68. The temperature of each heating zone of the heating chamberis detected by a thermocouple 69 as shown in FIG. 3 which iselectrically connected to a control unit 70. The control unit 70 issuesan instruction to drive the driving device 68 for opening or closingeach damper 66 depending upon the detected temperature so as to controlthe heating zone temperature to a preset temperature.

For example, each zone of the heating chamber is set to the followingtemperature:

    ______________________________________                                        zone I       140° C.- 160° C.                                   zone II      160°  C.-180° C.                                   zone III     180°  C.- 220° C.                                  zone IV      160°  C.- 200° C.                                  ______________________________________                                    

As shown in FIG. 3, the core metal 44 is held at the peripheral portionof the disk 45. As described previously, the pinion 54 provided at thelower end of the jig 25 is engaged with the gear 53. Thus, as the disk45 turns, the gear 53 also is rotated to give the core metal 44 arotation and revolution.

[SHIELDING PLATE]

As shown in FIG. 2, a shielding plate 71 is provided at the exit of theheating chamber 13. The shielding plate has radial fin members which arerotated synchronously with the movement of the core metal 44 to preventthe thermal atmosphere around the exit of the heating chamber 13 fromsuddenly being disturbed. The piece 10 which has advanced to the exit ofthe heating chamber 13 while being rotated is then moved while beingfenced by the fins and its rotation is stopped. In this case, the finsact to prevent a partical heating of the piece 10.

[BRAKING DEVICE]

At a position succeeding to the shielding plate 71 at the exit of theheating chamber 13, there is provided a braking device 73 for stoppingthe rotation of the core metal 44. As shown in FIG. 8, the brakingdevice 73 comprises a cam plate 74 and a spring. The cam plate 74 isbrought into contact with the cam follower 60 of the core metal 44 tobrake the rotation of the core metal in such a manner that the supportholder 57 of the core metal forces toward the center of the heatingchamber. The core metal 44 has its position controlled so that theunheld portion of the cylinder 32 of the jig 25 faces away from thecenter of the heating chamber so that it can be accurately held by theholding means 77 upon loading.

[LOADING APPARATUS]

As shown at the central part of FIG. 2, the loading apparatus 14comprises a mechanical manipulator having four rotary arms. That is tosay, four arms 76 are mounted an a rotatable shaft 75. Each arm 76 isprovided with a pair of holding means 77 at its free end. Also, each arm76 has a cam follower 79 which, as the rotatable shaft 75 is rotated,contacts a cam 78 so as to extend or contract the arm 76 and to open orclose the holding means 77 in accordance with the configuration of thecam 78.

At a position somewhat advanced from the exit of the heating chamber 13,the holding means 77 are closed, and the jig 25 is removed from the coremetal 44 and the arm 76 is contracted towards the shaft 75. Then, thearm 76 is extended to its initial length while being turned in thedirection of arrow 80. An arcuate guide rail 81 for guiding the rotationof the holding means 77 is provided along the circumference of thesemicircle drawn by the free end of the arm 76. On the inner surface ofthe guide rail 81, there is mounted a magnetic piece for attracting andholding the cylinder 32 of the jig 25 so that the jig 25 is rotated toprevent the partial cooling of the piece 10 when the arm 76 turns. Thepiece 10 with the jig 25 held by the free end of the arm 76 is placed inthe mold 72, where the jig 25 is released from the holding means 77 andinserted into the cavity 87 of the mold 72. From that position where thepiece 10 is inserted into the mold 72, through the circumference of thesemicircle opposite to the guide rail 81, to the other position wherethe braked and stopped jig 25 is caught, the holding means 77 on the arm76 maintain their opened state. When the jig 25 held by the holdingmeans 77 is pulled towards the shaft 75, the piece 10 held on theopposite arm is charged in the mold.

ORIENTATION-BLOW MOLDING MACHINE

The orientation-blow molding machine 15 is of a rotary station type, inwhich the mold 72 is provided at each of eight stations on a turntable82. However, it is to be noted that the number of stations are notnecessarily limited to eight as in the illustrated embodiment, but tenor more stations may be provided as well.

As shown in FIG. 9, the mold 72 comprises two mold halves 83 and 84separable in the longitudinal direction and an upper mold member 85. Onemold half 83 is fixed, while other mold half 84 is pivotally movableabout a pivotal shaft 86 as shown in FIG. 2. The mold 72 is opened atthe first and eighth stations, while it is kept closed at the secondthrough seventh stations. As a matter of course, the upper mold member85 is moved upwardly and downwardly correspondingly as the mold 72 isopened and closed.

Beneath the mold 72, there is provided a cylinder rod 88 which pushes upthe core shaft 30. A compressed air introducing hole 89 islongitudinally passed through the cylinder rod 88. The cylinder rod 88pushes up the core shaft 30 at the second station for longitudinallyorienting the piece 10 and compressed air is introduced through the hole89 into the piece 10 at the third station for laterally orienting thesame. Thereafter, the cylinder rod 88 is lowered at the seventh station.

[UNLOADING]

The mold 72 is opened at the eighth station of the blow molding machine,where the jig 25 holding the biaxially oriented product is exposedoutside. Then, the cylinder 32 of the thus exposed jig 25 is caught by apair of holding means 90 of the unloading equipment 16 having two rotaryarms to be taken out from the mold 72. The unloading equipment 16 hasits two arms 92 extended diametrically from a member supported on a itsrotatable shaft 91, and the openable and closable holding means 90 aremounted at the free ends of the arms 92. The jig 25 taken out from themold 72 at the eighth station is held by the holding means 90 and movedalong the direction of arrow 93 to be caught by the hook 23 of theconveyor 11, where the container 20 is removed from the jig 25.

[OPERATION]

First, an empty jig 25 is transferred by the conveyor 11 as shown inFIG. 2 to the setting position, where the injection-molded piece 10 ismounted onto the jig 25 in its inverted position, as shown in FIG. 5.The piece 10 has its neck opening 18 gravitationally inserted into thegap 27a between the neck support 27 and core guide 28 of the jig 25. Forthis purpose, a depressing means (not shown) which functions tointerlock with the transfer apparatus 12 is provided at a positionimmediately succeeding to the transfer apparatus for lightly pushingdown the piece 10 from above to ensure that its neck opening 18 isfitted in place onto the jig 25.

The transfer apparatus 12, with a swing motion of its arm 40, transfersthe jig 25 holding the piece 10 to the core metal 44. The apparatus 12is provided with a guide rail 42 having a magnetic piece and drawing agentle arc.

The jig 25 mounted onto the core metal 44 by the transfer apparatus 12is gravitationally engaged therewith in the state as shown by the chainline in FIG. 6 and moved through the heating chamber 13 while having arotation and revolution imparted thereto from the gear 53 and pinion 54.

In this case, as described previously, such a jig that cannot besufficiently engaged by gravity with the core metal due to strongmagnetism of the magnet piece 59 of the core metal 44 is lowered to apredetermined position by pushing down the upper end of the piece withthe afore-mentioned depressing means (not shown).

After entering the heating chamber 13, the jig 25 is advanced from theentrance near the transfer apparatus 12 towards the exit of the chamber13 while being rotated by the rotation and revolution of the core metal44. In the heating chamber 13, the piece 10 mounted on the jig 25 isheated in sequence at the respective heating zones to render optimumtemperature conditions for the succeeding orientation process. Asmentioned previously, two or three heating tubes 62 are horizontallyprovided on the inner side of each heating zone, while several verticalheating tubes 63 are provided on its outer side. These are necessarybecause the temperature will be undulatingly distributed along thevertical direction of the piece 10 if only the lateral heating tubes areused, while a chevron-like distribution having its peak at thelongitudinal center of the piece and gradually reduced temperaturestowards its upper and lower ends will appear if only the verticalheating tubes are used. Thus, in the blow molding equipment according tothe present invention, a combination of vertical and horizontal heatingtubes are adopted to secure an even and uniform temperature distributionover the entire piece. These heating tubes 62 and 63 are mounted by theuse of an assembly 95 (FIG. 3) with stands and screws so that theirmounting positions can be finely adjusted both laterally andlongitudinally and both in the vertical and horizontal directions. Theheating chamber 13 thus heated by the vertical and horizontal heatingtubes 62 and 63 has its temperature adjusted by the operation of theheat-exhausting damper 66 provided on the top of the cover. That is tosay, the temperature of each heating zone of the heating chamber 13 isdetected by the thermocouple 69, as shown in FIG. 3, which is connectedto the control unit 70. The driving device 68 is actuated by aninstruction from the control unit 70 for opening or closing the damper66 to correspondingly control the temperature of the heating zone.

The piece 10 evenly heated in the heating chamber 13 is advanced towardsthe exit of the chamber 13 while being rotated and, when the core metal44 comes up to the braking device 73 provided adjacent to the shieldingplate 71, the cam follower 60 comes into contact with the cam plate 74and core metal 44 is stopped with the non-contacted portion of cylinder32 of the jig 25 being positioned to face away from the center of theheating chamber 13.

The core metal 44 thus stopped by the braking device 73 actuates theejector pin 50 provided below to move the jig 25 upwardly and, at thesame time, closes the holding means 77 of the loading equipment 14positioned at that position where the core metal 44 is stopped forcausing the holding means 77 to catch the cylinder 32 of the jig 25.Then, the arm 76 is contracted and pivotally moved along the guide rail81 to fit the jig 25 into the cavity 87 of the mold 72. The guide rail81 has a magnet piece which attracts and holds the cylinder 32 of thejig 25 for continuously rotating the same as it is pivotally moved bythe arm 76.

As described previously, in the illustrated embodiment mold 72 has eightstations. The jig 25 onto which the heated piece 10 is mounted is placedinto the opened mold 72 and the mold is closed at the first station.Then, as the mold 72 is being moved towards the second station, the coreshaft 30 is pushed upwardly to longitudinally orient the piece 10. Sincethe core shaft 30 has a core top 35 of inverted taper shape, the piecewill not be punctured by the core shaft 30. Thus the piece 10 islongitudinally oriented properly by the core shaft as it is pushedupwardly.

Then, as shown in FIG. 10, compressed air is introduced through the airpassage 39 formed in the core shaft 30 into the piece 10 for laterallyorienting the same.

The air passages 39 are formed as spline grooves on the outside of thecore shaft 30. Instead of the spline groove, a longitudinal hole openedat the side may be bored through the center of the core shaft 30.However, in a core shaft of such a hollow structure, the core shaft 30cannot have a sufficient wall thickness and its mechanical strength willbe insufficient when it is pushed up under high blow pressure such as 50kg/cm² or above. In addition, if compressed air is blown out throughpores formed orthogonally or obliquely in the side wall of such a hollowtype core shaft, compressed air will cause dimple flaws on the moldings.Such dimples will remain and damages the commercial value of thecontainer.

Alternatively, instead of the spline several air passage grooves may beformed in the inner peripheral surface of the core guide. However, sucha structure has working disadvantages.

In the second through seventh stations, the mold and jig are kept in thestate as shown in FIG. 10. At the eighth station, the mold 72 is openedand the jig 25 holding a molded piece is taken out of the mold 72 by theunloading equipment 16 having two arms as shown in FIG. 10. As describedpreviously, the unloading equipment 16 is provided with the rotatableshaft 91 having positioned diametrically two arms 92 at its upper end.The arms 92 have holding means 90 at their free ends. The unloadingequipment 16, with its holding means 90, catches the jig 25 at theeighth station and transfers it to the conveyor 11.

After being transferred to the conveyor 11, the molded piece (container)is moved upwards to be released from the jig 25. Then, the emptied jig25 is carried by the conveyor 11 in the direction of arrow 96 and,during the course of this, a new injected parison (piece) is mountedonto the jig 25, and the new piece undergoes the same processings ofheating and orientation as those undergone by the previous piece.

FIG. 11 shows a product container 20 molded by the orientation-blowmolding equipment according to the present invention. As shown in FIG.10, the container 20 has a neck opening 18, a cylindrical barrel 20bhaving almost the same diameter throughout its length and a shoulderportion 20a extending between the neck opening 18 and barrel 20b in agradually increasing diameter from its top to its bottom. As describedpreviously, this container is produced by heating an injection-moldedpiece and orienting it first longitudinally and then laterally. Itsbarrel portion has almost an uniform wall thickness and the containerhas an improved transparency and excellent impact resistance owing tothe biaxial orientation.

As fully described hereinbefore, since the orientation-blow moldingequipment according to the present invention can heat the injectedparison (injection-molded piece) evenly and accurately orient itlongitudinally as well as laterally in the mold, plastic containershaving an improved toughness, strength and transparency can be easilyproduced by it. Also, since the heating chamber is divided into severalheatings zones so that the piece can be heated at temperatures which arecontrolled stepwise, a heating operation under optimum temperatureconditions for the succeeding orientation process is feasible. Further,since the piece mounted on the jig is rotated in the heating chamber forensuring an even and uniform heating, protected by the shielding plateat the exit of the heating chamber to avoid a partial heating and thenput by the loading equipment into the orientation-blow molding machineof rotary statiin type, the molding accuracy can be improved in that thepiece can maintain its heating temperature until the orientation andmolding process.

In addition, since a jig which has a neck support, mandrel and coreshaft and can hold the piece with its neck opening positioned down inthe gap between the neck support and core guide, the mounting of the jigonto the core metal in the heating chamber, its mounting onto the moldof the molding machine after its being taken out from the heatingchamber and its removal from the mold can be performed more smoothly.Thus the containers can be produced at a higher efficiency with animproved molding speed.

What I claim is:
 1. Equipment for producing biaxially orientedcontainers comprising:a jig having a neck support which can hold theneck of a plastic piece positioned upside down, a mandrel providedbeneath said neck support, and a core shaft for longitudinal orientationof said piece which is provided inside said mandrel so as to be freelymovable upwardly or downwardly and which has a blow-molding air passage;a core metal movable in a continuous path in a heating chamber, saidcore metal having a cylindrical holder, a hollow shaft freely rotatablysupported at the center of said cylinder, a cylinder provided at theupper end of said shaft, a support holder extending from the top of saidcylinder for supporting said mandrel of said jig, and a gear provided atthe lower end of said shaft for transmitting a rotational motion; saidheating chamber having a rotary disk to which a plurality of said coremetals are attached, said heating chamber being provided with severalsets of heating elements and heat-exhausting damper devices so as toprovide therein several heating zones along the transfer passage of saidcore metals attached to said rotary disk for heating stepwise said piecemounted on said jig; a shielding plate having radial fins which arerotated in association with the movement of said core metal forpreventing thermal atmosphere at the exit of said heating chamber frombeing suddenly disturbed and preventing a thermal influence on thepiece; a support holder braking means for stopping the rotation of saidcore metal, said braking means being provided at a position apredetermined distance apart from said shielding plate in the directionof the rotation of said rotary disk; a mold loader which catches saidjig holding the thermally processed piece for loading the same from thecore metal which has stopped rotating by the action of said supportholder braking means to a blow molding machine of rotary station type; ameans for rotating said jig while transferring said jig from saidheating chamber to said molding machinery; a blow molding machine ofrotary station type having a plurality of molds and provided beneathsaid molds with a cylinder rod for pushing upwardly said orienting coreshaft of said jig placed in each said mold and for introducingcompressed air into the same; a mechanism for pushing up said coreshaft; an unloading means for taking out said jig from said mold placedat the final station of said blow molding machine; a conveyor having aplurality of attachment hooks for removing the jig from said unloadingmeans to release the molded container from said jig and for catching themandrel of the thus released jig to mount a new piece thereonto; and atransfer apparatus provided at a corner of said conveyor for mountingsaid jig which has advanced to said corner onto the core metalpositioned at the entrance of said heating chamber.
 2. Anorientation-blow molding equipment according to claim 1, wherein anejector pin is inserted in said shaft of said core metal to moveupwardly said jig which has advanced to said loader for ensuring apositive holding of said jig while loading, a position opposite to theposition where said support holder is mounted on said cylinder.
 3. Anorientation-blow molding equipment according to claim 1 or 2, whereinsaid support holder of said core metal is provided with a magnetic piecefor attracting the mandrel of said jig to ensure a positive holding ofsaid jig.
 4. An orientation blow molding equipment according to claims 1or 2, wherein said support holder of said core metal has a width equalto half a diameter of said cylinder and a length slightly longer thanthat of said mandrel of said jig and wherein an arcuate projection onthe top of said support holder engages with a shoulder of said mandrelof said jig.
 5. An orientation-blow molding equipment according to claim1, wherein a temperature detecting means is provided in each of saidheating zones of said heating chamber and a control unit is provided forcontrolling the temperature of said heating zone by comparing the thusdetected temperature with a preset temperature to correspondingly drivesaid heat-exhausting damper.
 6. An orientation-blow molding equipmentaccording to claims 1 or 2, wherein said heating elements provided ineach heating zone of said heating chamber each comprise an infraredheating tube of bar type and a plurality of tubes are disposedhorizontally and a plurality of tubes are disposed vertically in eachheating zone.
 7. An orientation-blow molding equipment according toclaim 1, wherein said support holder braking device comprises an arcuatecam plate and a spring which are provided at the exit of said heatingchamber so that the cam follower of the core metal is brought intocontact with said cam plate for stopping the rotation of said jig alwaysin a position in which said jig supported by said support holder of saidcore metal faces away from the center of said heating chamber.
 8. Anorientation-blow molding equipment according to claim 1, wherein saidloader has four arms which can be extended or contracted by the actionof a cam and a pair of freely openable and closable holding means aremounted on the free end of each said arm for holding said mandrel as itis moved from the exit of said heating chamber to the mold, an arcuateguide rail having a magnetic piece for rotating the jig being providedalong the periphery of a circular course which is traced by said jigholding means.
 9. An orientation-blow molding equipment according toclaim 1, wherein said unloading equipment is provided with a pair ofholding means for catching said jig by cam action and holding the sameas it is moved from said mold placed at said final station to saidconveyor.
 10. An orientation-blow molding equipment according to claim1, wherein said transfer apparatus comprises an arm which is pivotallymoved around a fulcrum, a hook provided at the free end of said arm anda guide rail having a magnetic piece and disposed along the periphery ofthe course traced by said hook.